The invention relates to a drive arrangement for at least one auxiliary equipment of an internal combustion engine having an engine block and a rotating output member, wherein the drive arrangement comprises an epicyclical gear having three main components consisting of or comprising a sun gear, a ring gear and a planet carrier, and wherein:                a first component is to be connected to the engine rotating output member,        a second component is to be connected to the rotor of a first electric machine having also a stator, and        a third component is to be connected to said at least one auxiliary equipment.        
Such a drive arrangement can be especially used for an engine installation mounted on a vehicle, where the engine is the vehicle's traction engine, but also for stationary engine installations. Document U.S.-2008/0020887 discloses a drive arrangement of the type above. Such an arrangement is very useful in order to be able to adapt the speed of the auxiliary equipment independently of the speed of the traction engine. Indeed, in previous drive arrangements, the accessory would be in most cases directly driven by the engine, through a constant speed ratio transmission. Therefore, the speed of the auxiliary equipment would follow the speed of the engine. Unfortunately, in many cases, there is not a direct connection between the optimal speed profile of the auxiliary equipment and the optimal speed profile of the engine. Basically, in a vehicle, engine speed is linked to the vehicle speed. Therefore, when the vehicle is running at high speed, the engine is also operating at a relatively high speed. On the other hand, it may at that time not be necessary to drive the accessory at high speed. For example, an engine cooling fan does not need to operate when the vehicle is at high speed, simply because the air flow due to the vehicle speed is in most cases enough for achieving the necessary cooling of the engine. Similarly, an alternator delivering electricity to on-board accessories does not necessarily need to deliver its full power if, at the same time, the main electric consumers, such as the headlights, the defogging resistors, the windshield wipers, etc., do not operate. Of course, engine speed is also related to which gear of the gearbox is engaged, which, in many cases, has no direct connection with the needs of the auxiliaries. Therefore, in many cases, previous systems with direct drive of the auxiliary equipment by the engine tend to generate power losses because the auxiliary equipment is not driven at the right speed. Inversely, auxiliary equipment sometimes needs to be over-designed to deliver sufficient performance while driven at low speeds when the engine is at low speeds. Therefore, a drive system as in U.S.-2008/0020887 has the great advantage that it allows operating the auxiliary equipment at a more appropriate speed, whatever the instant operating speed of the engine. Nevertheless, the drive system as in U.S.-2008/0020887 is quite complex in terms of its number of parts. Also, several parts of the system, which need to be aligned because they cooperate via gearings, are mounted on different static parts, so that, to ensure proper alignment, very stringent dimensional requirements are needed for the system to operate properly.
Document DE-102.14.637 discloses a similar type of drive arrangement. This drive arrangement is dedicated to driving a pump. The design of the drive arrangement is adapted to the fact that such a pump is rigidly fixed to the engine through its casing. The drive arrangement is therefore build around the casing of the pump. Similarly, very stringent dimensional requirements appear necessary for the many parts of the system to be properly aligned.
In view of the above prior art, there remains a need for a drive system of type described above, but with an architecture capable of being embodied in a simpler manner.
According to an aspect of the invention, a drive system of the type described above is characterized in that said first component which is to be connected to the engine rotating output member is guided in rotation by a strict pivot connection on the engine block and comprises a rigid assembly which supports the other two components, in that the stator of the first electric machine is fixed on a holder, said holder being guided in rotation by a strict pivot connection directly or indirectly on said first component rigid assembly, and in that the first component is guided in rotation on the engine block independently from the holder.